ANS a)
When the secret message is converted in a vector form and passed through the system matrix we get the encrypted message.Again the encrypted message is multiplied by the inverse of the system matrix,to get the decrypted message.The inverse is multiplied first by the set of first 3 numbers in the matrix,then multiplied by 2nd set of 3 num and then 3rd set of 3 numbers and the results of the above three are taken in a vector form.Each element of the vector is then replaced by its correspinding alphabet to get the decripted message..This is how BOB bets the decripted message.
Ans b)
No,eve wont be able to decript the message without knowing the martix.The inevrse matrix will only hept her to ceript the message
